Callback {
  constructor(call: Call, listener: EventSourceListener) : this(call, call.request(), listener)

  constructor(response: Response, listener: EventSourceListener) : this(null, response.request, listener)

  @Volatile private var canceled = false

  override fun onResponse(
    call: Call,
    response: Response,
  ) {
    processResponse(response)
  }

  internal fun processResponse(response: Response) {

  private var expectMoreExchanges = true

  // These properties are accessed by canceling threads. Any thread can cancel a call, and once it's
  // canceled it's canceled forever.

  @Volatile private var canceled = false

  @Volatile private var exchange: Exchange? = null
  internal val plansToCancel = CopyOnWriteArrayList<RoutePlanner.Plan>()

  override fun timeout(): Timeout = timeout